British Prime Minister David Cameron, center, Melinda Gates and British International Development Secretary Andrew Mitchell talk with activists during the London Summit on Family Planning on July 11, 2012

Melinda Gates wants to put birth control back on the agenda. In May, the billionaire philanthropist announced she plans to make family planning her signature, promising billions of dollars to promote contraceptive use, particularly in poor nations. Today, at the London Summit on Family Planning, co-hosted by the Bill & Melinda Gates Foundation and the U.K., she put the plan into action, officially launching a $4 billion fundraising campaign. It is being billed as landmark show of support for an issue that has long languished on the margins of development policy. Here, quickly, are three things you should know:

1.This is big. And not just because of the money. Decades of research show, conclusively, that improving access to contraception is good for women, good for children, good for countries. Yet over the past 15 years, support for family-planning programs has plummeted. The redirection of development funds to HIV/AIDS programs explains some, but not all, of the drop. Coercive campaigns like China’s one-child policy and forced sterilizations in India have fostered suspicion about state-backed population programs. Conservative religious groups, particularly in the U.S., have tried to link family planning to forced abortion. In 2002, President George W. Bush cut funding to the U.N. Population Fund completely, turning birth control into a bad word. The cause has yet to recover. Backing from Gates, a Catholic who is respected by conservatives and liberals alike, could turn this around.

2. This could save lives. A Johns Hopkins University study published this week in a leading medical journal, the Lancet, estimates that contraceptive use prevents 272,000 maternal deaths per year. And yet, according to U.N. research, an estimated 220 million women have an unmet need for modern family planning. The Gates Foundation hopes to address this gap. If it succeeds, lives will be saved.

3. This is only the beginning. Family planning is not a panacea. The London Summit and the Gates Foundation’s pledge are positive steps, but it is important to remember that contraceptives alone are not enough. Women need condoms and pills, yes, but they also need to have the power to use them — or not use them — as they wish. They need decent medical care and access to safe abortions. Without this, all this, the battle won’t be won.

Rauhala is an Associate Editor at TIME. Find her on Twitter at @emilyrauhala. You can also continue the discussion on TIME’s Facebook page and on Twitter at @TIME